Most wireless receivers employ automatic frequency control (AFC) for the fine tuning of the internal frequency synthesizer to the carrier frequency. In the prior art, the frequency of the carrier is usually measured with a resettable counter, which counts the number of zero-crossings of the input signal over a given period of time. In order to achieve a high accuracy with this method it is necessary to employ a high-order counter. Moreover, reset of the counter introduces a quantization error.
There exists, therefore, a need in the art for a system of automatic frequency control which can be implemented by a lower-order counter and which is not susceptible to quantization error.